A vehicle driveshaft connects the transmission to a distant wheel axle. This is most commonly done in rear-wheel drive (RWD) and all-wheel drive (AWD) vehicles. The driveshaft can move vertically with respect to a vehicle frame during normal driving conditions. For example, as shown in FIGS. 1 and 2, the angular disposition of a forward section of the driveshaft rotates in different directions depending on the loading conditions of the vehicle. Driveshaft components, however, are designed to operate within a preferred angular range. Many vehicles with rear or all-wheel drive systems are designed for a standard payload so that the driveshaft is angularly disposed at a preferred position. Known suspension damping or performance characteristics can also influence this. Angle fluctuation outside of the design standard can cause objectionable vehicle shudder.
Some vehicles, such as pick-up trucks, have multi-piece drivelines with a center bearing support that sections the driveshaft into shorter tubes between Universal joints. The angle of a rear most section changes with axle height and the center bearing height, as shown in FIGS. 1 through 3.
Several types of angle fluctuation mitigation schemes are used in the industry to manage joint angles under different operating conditions. Some methods include: (i) shimming the axle to a suspension interface; or (ii) offering powered center bearing brackets or adapters to adjust the height. For example, U.S. Pat. No. 4,966,251 titled “Automotive Vehicle with Center Bearing of Propeller Shaft Assembly Variable in Position” discusses a pneumatic adjuster controlled through an electrically powered servo valve according to vehicle operating conditions. U.S. Pat. No. 6,345,680 titled “Electrically-Controlled Adjustable Height Bearing Support Bracket” discloses an electric motor that drives adjustment of the bearing support. Performance of these electrically powered systems can be limited to the narrow tuning range of known axle-suspension travel. Moreover, electrically driven systems are relatively expensive to implement and maintain, thus adding to the overall complexity and costs of vehicle manufacture and repair.
Shimming the driveshaft would not allow for a real-time or automatic adjustment of driveshaft position. For example, today driveshaft positions can be tailored to fit known loading conditions for a particular user. However, when the vehicle is operated outside of the tailored use the pre-set driveshaft position is less effective.
Therefore, it is desirable to have a real-time or load dependent, self-actuated, self-powered height adjustment mechanism for the vehicle driveshaft.